The present invention relates to a seatbelt retractor for retracting a seatbelt to constrain and protect a passenger in a vehicle such as an automobile. More specifically, the present invention relates to a seatbelt retractor capable of controlling a belt tension of the seatbelt by rotating a spool with a motor power and having an energy-absorbing mechanism (hereinafter, also referred to as EA mechanism) for absorbing shock energy exerting on a passenger caused by the seatbelt when the seatbelt is prevented from being withdrawn in a case, for example, where a car undergoes large deceleration due to a crash or the like. The present invention also relates to a seatbelt device provided with the seatbelt retractor.
A seatbelt apparatus attached to a seat in a vehicle such as an automobile includes a seatbelt retractor for retracting a seatbelt on a spool. As such a retractor, a variety of emergency locking retractors (hereinafter, also referred to as ELRs) have been developed. In case of emergency when large deceleration of a car occurs due to a car crash or the like, the ELR detects the deceleration, and a locking mechanism prevents the spool from rotating in the belt-withdrawing direction. Accordingly, the seatbelt is prevented from withdrawal caused by a passenger moving forward due to inertia, so that the ELR more reliably constrains and protects the passenger.
In such an ELR, when the locking mechanism prevents the spool from rotating in the belt-withdrawing direction so that the seatbelt constrains and protects the passenger, the passenger receives a large shock from the seatbelt. Although the shock does not cause a serious problem against the passenger, it is desirable to absorb the energy of the shock so as to limit an impulsive force.
An ELR in which an energy-absorbing mechanism (EA mechanism) is disposed to absorb the shock energy and limit a load exerted on the seatbelt in the event of the foregoing emergency in a seatbelt-wearing state has been developed. A seatbelt retractor including the EA mechanism and having a torsion bar interposed between a spool and a locking mechanism has been proposed (refer to Japanese Patent Publication (Kokai) No. 07-47923). In the seatbelt retractor disclosed in Japanese Patent Publication (Kokai) No. 07-47923, one end of the torsion bar is fixed to the spool so as to be rotatable together with the spool, and the other end of the torsion bar is fixed to a pawl-supporting member (hereinafter, referred to as locking base) supporting a pawl of the locking mechanism so as to be rotatable together with the pawl member. In the event of the foregoing emergency, the pawl of the locking mechanism engages a frame so as to prevent the locking base from rotating in the belt-withdrawing direction. Since the spool rotates in the belt-withdrawing direction due to inertia of the passenger, the torsion bar is deformed, and the foregoing shock energy is thus absorbed.
A motor-driven ELR in which a seatbelt is retracted by rotating a spool with a power of a motor has been proposed (refer to Japanese Patent Publication (Kokai) No. 2000-95064). Since the ELR disclosed in Japanese Patent Publication (Kokai) No. 2000-95064 controls a tension of the seatbelt by retracting the seatbelt with the motor, a passenger is appropriately constrained by the seatbelt in accordance with a car-running situation and so forth.
A seatbelt retractor in which the motor-driven ELR is applied to an ELR including the foregoing torsion bar has been proposed (refer to Japanese Patent Publication (Kokai) No. 2000-95064). In the ELR disclosed in Japanese Patent Publication (Kokai) No. 2000-95064, when there is a risk of a car crash, tension of a seatbelt is increased by driving a motor before activation of a locking mechanism of the ELR so as to constrain a passenger, and then, when the locking mechanism is activated, the torsion bar is deformed as described above so as to absorb the shock energy. With this structure, in case of emergency, the passenger can be effectively constrained and protected without suffering a large shock.
In the seatbelt retractor disclosed in Japanese Patent Publication (Kokai) No. 2000-95064, the motor is directly connected to the spool through a power transmission system. After the locking mechanism is activated, when the spool rotates in the belt-withdrawing direction and the torsion bar is deformed, the spool receives a certain amount of resistance from the motor and the power transmission system. The shock energy transmitted to the torsion bar is somewhat reduced by an amount corresponding to the resistance. The reduction does not particularly deteriorate a shock absorbing effect of the torsion bar, thereby achieving a satisfactory shock absorbing effect. Nevertheless, it is desirable to reduce such a resistance as small as possible so as to achieve a more satisfactory shock absorbing effect.
In view of the problems described above, the present invention has been made, and an object of the present invention is to provide a seatbelt retractor in which the shock energy is more effectively absorbed by a torsion bar included in a motor-driven ELR.
Further objects and advantages of the invention will be apparent from the following description of the invention.